The information provided herein and references cited are provided solely to assist the understanding of the reader, and does not constitute an admission that any of the references or information is prior art to the present invention.
Occupants of buildings located in warm weather climate zones often expend substantial amounts of energy to cool the interior of the building, e.g. air conditioning. One way to reduce energy consumption and energy demand is to employ energy-saving coatings on the building's exterior. Typically, these coatings act to reduce heat load to a building by reflecting away sunlight and/or by blocking the transfer of heat. These coatings have the purpose of reducing a structure's heat gain when the weather is hot, and heat loss when weather is cold.
Energy costs, in some cases, can be significantly reduced with the use of some energy-savings coatings. However, the amount saved can vary and is dependent on the building structure itself, i.e. age, condition, color, insulation already present, etc. The environment also exerts a significant influence. For instance, those in hotter climates may notice more savings than those in cooler areas. “In fact, assessing potential energy savings is somewhat of an art as well as a science” (Mills-Senn, P., “The Sun”, PWC, January–February 2004, p. 53–75; quoted citation on p. 54; the entire disclosure of which is incorporated herein by reference).
Energy-savings coatings can be described in terms of its reflectivity or reflectance property, which indicates the degree to which a coating reflects light, e.g., percentage of light that is reflected away from the surface. Another characteristic property is emissivity, which can be defined as the ability of a surface to radiate or emit energy in the form of longwave infrared radiation. Emissivity is represented by a value ranging from zero to one, wherein values closer to one correlate with lower effectiveness of the surface at impeding radiant heat transfer. For example, a coating with an emittance value of 0.25 will be more effective at blocking radiant heat transfer than a coating that has an emittance value of 0.75.
Energy-saving coatings are most typically applied to roofs on the roof's exterior or to its underside, and are generally referred to as “radiation control coatings” or “radiant barriers” for interior roof coatings. Additionally, energy-saving coatings can also be applied to exterior and interior walls in much the same way as those used on roofs (Mills-Senn, P., supra, see p. 53).
The following are examples of energy-saving wall and/or roof coatings (Mills-Senn, P., supra, see p. 67–68).
Nationwide Chemical Coating (Bradenton, Fla.) manufactures a line of elastomeric ceramic reflective wall coatings under the name Ultra Seal, Ultra Satin, and Ultra Kote. The ceramics in these coatings provide the additional benefit of dissipating heat buildup more efficiently.
SPM Thermo-Shield (Custer, S.D.) manufactures wall coatings under the Thermo-Shield brand which uses hollow, vacuumed ceramic bubbles as the primary filler. The Thermo-Shield coatings are tintable, although white is the recommended color for best energy savings.
Advanced Coating Systems (Atlanta, Ga.) manufactures reflective acrylic elastomeric wall coatings that are primarily white but can be tinted. These coatings dry to a rubber-like film that is flexible and water-proof.
Cerama-Tech International (San Diego, Calif.) manufactures a ceramic coating that is reflective, emissive, and elastomeric, that can be sprayed onto any exterior or interior paintable surface. The coating is white but can be tinted to almost any mid-range color.
Sherwin-Williams manufactures a one-part latex-based coating designed for residential attics, decking, and coated commercial metal decking. The coating, marketed under the name E-Barrier Reflective Coating, reflects radiant energy via microscopic metal particles.
The following disclosures describe reflective coatings, compositions, or materials.
U.S. Pat. No. 4,916,014 reports infrared reflecting compositions for coating of structures exposed to sunlight which reduce heating of the structure by the sun. Infrared reflecting materials described include metals, such as noble metals, zinc, nickel, copper, or aluminum.
U.S. Pat. No. 6,004,894 reports porcelain enamel compositions for use in forming infrared reflective coatings comprising a glass component and a cerium oxide component.
U.S. Pat. Nos. 6,174,360 and 6,454,848 (the disclosures of which are incorporated herein by reference) report building materials, such as stucco, roofing tiles, roofing granules, roofing shingles, or brick, comprising infrared reflective pigments having a corundum-hematite crystalline structure.
U.S. Pat. No. 6,468,647 report infrared reflect visually colored metal substrates or metal-coated particles prepared by burnishing colored pigments into the metal.